Belgium, America's Third Largest Creditor [Sort Of]

While researching the previous post, I came across a seemingly astounding finding: Unbeknownst to most, a European country has somehow gained a podium place in the international suckers' competition known as "Major Foreign Holders of [US] Treasury Securities." Topping these hosers was China with a GDP of $8.358 trillion, followed by Japan ($5.96 trillion) and, er, Belgium (483.7 billion)[?!]. $310.3B worth of Treasuries is nothing to sneeze at.

The usual suspicion with high-placing Treasury holders without much reason for being there is that others course their transactions through them to disguise their motives and, consequently, their holdings. In past years, the United Kingdom has served this purpose as a lightly regulated money center. Reports would indicate massive UK holdings, which were eventually heavily revised downwards during following months. At present, Caribbean offshore entities still perform this function, ranking a combined fourth overall among Treasury holders.

So, is Belgium becoming the next major offshore economy? Especially since the European banking crisis, regulations there have certainly tightened, not loosened. What's more, Brussels does not usually count as a financial center--not even for Western Europe. What, then, is going on here? After consulting IPE stalwart Thomas Oatley over at UNC, he points me in the direction of Euroclear, a massive clearinghouse headquartered in Brussels that was established to facilitate trade in Eurobond markets in the late Sixties. Since then, it has if anything else increased the scale of its operations and now boasts "[e]very 6 days we settle
transactions equivalent to the GDP of the EU":

We help you to be more successful by making it easier for you to
settle domestic and cross-border securities transactions and safekeep
your investments. We also help you manage the risks and exposures
arising from your transactions.

The assets we hold for you are valued at €23 trillion. The total
value of securities transactions settled for you by the Euroclear group
is over €540 trillion per annum. Our multi-lingual, highly trained team
of professionals based in Europe, Asia, the Middle East and the Americas
are committed to providing personalised support

OK, so this appears to be a plausible hypothesis: someone is using Euroclear to course a large amount of Treasury purchases. If so, then we have two more questions. First, what country or countries are these? Next, what reasons do they have for disguising their purchases by coursing Treasury purchases through Belgium? These are mysteries that will reveal themselves as matters unfold. Obviously, Russia figures large in the minds of some--including Tyler Durden (the Fight Club protagonist?) at Zero Hedge.

So no, a European country populated by folks with anarcho-syndicalist tendencies is prolly not lending China/Japan-like jillions to the US. Go somewhere else for conspiracy theories. Sorry.
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As an aside--this being the weekend--I am keen on Belgium going far in the World Cup with a talented young squad. I might've taken a punt (Britspeak for "bet") on Belgium but they're currently the fifth most-favored team to win the event.